core, citra_qt: Allow credentials update in multiplayer announce session

Allows updating the credentials of the announce session, thus allowing credentials changes to be reflected before citra restart. To avoid race conditions and web errors (you can only update the room that you created, i.e. changing credentials halfway will make it break), now you can only use the Citra Web Services settings when not hosting a public room.

src/citra_qt/configuration/configure_web.h

@@ -22,6 +22,7 @@ public:
     void applyConfiguration();
     void retranslateUi();
     void setConfiguration();
+    void SetWebServiceConfigEnabled(bool enabled);
 
 private:
     void RefreshTelemetryID();